1. Technical Field
The present invention relates to a pharmaceutical preparation which is stable to light (especially ultraviolet rays) or heat, and which has excellent storage-stability; and a coating agent which is a raw material of such a pharmaceutical preparation.
2. Background Art
It has been found that O.sup.6 -benzylguanine is decomposed in an aqueous solution of polyethylene glycol 400 at room temperature by the reaction of formaldehyde (present as an impurity of polyethylene glycol 400 and probably produced by air oxidation of polyethylene glycol 400) with O.sup.6 -benzylguanine [Pharmaceutical Research, 11 (7), 1060-1064 pp. (1994)].
JP-A-63-301816 (EP-A1-0277741) mentions an enteric coating using an enteric film-liquid including titanium oxide and polyethylene glycol 6000.
Chemical Abstracts 122:388853 mentions tablets containing vitamin C, Yinqiao extracts, acetaminophen, chlorphenramine, calcium carbonate, starch, dextran, peppermint oil and Yinqiao and jingfang volatile oils coated with a composition containing hydroxypropylmethyl cellulose, no.2 enteric vinyl resin, PEG 6000, sesame oil, Tween 80, titanium oxide, talc, Mg stearate, food color, 95% ethanol, and distilled water.
JP-A-63-166824 mentions soft capsules comprising oily solution containing pharmaceutically active ingredient unstable in light, coated with a coating agent containing fine particles of titanium oxide of at least 85% with particle size of 0.1 .mu.m or less.
When a pharmaceutical preparation which is unstable to light is provided to consumers, the pharmaceutical preparation has to be wrapped or coated for protection from light. However, when storage conditions of a pharmaceutical preparation at a pharmacy in a hospital or at patients are considered, it is difficult to say that sufficient quality of the pharmaceutical preparation is guaranteed by wrapping for protection from light. Therefore, when a pharmaceutical preparation which is unstable to light is manufactured, coating for protection from light is desired.
However, in case of manufacturing a pharmaceutical preparation comprising a drug which is unstable to light, when a tablet comprising the drug was coated with a coating agent which comprises an agent for protection from light such as titanium oxide and a plasticizer such as polyethylene glycol, there was a problem that the obtained film-coated tablet was less stable to light than before coating.